Commercial photographic printers are devices capable of exposing photographic positive paper in response to illumination from photographic negatives. These processes are well-known in the art. Because of the economies of scale, it is desirable to print photographs in a commercial environment as quickly and accurately as possible. In the past, commercial photographic printing equipment utilized manual techniques for transporting large reels of film through the printer. Typically a printer operator would hand crank a "take-up" reel to pull a roll of negatives from a feed reel, across the exposure window or "gate" and the frame of the printer. This system was prone to operator error and damage to the film. Accordingly, efforts were undertaken to develop an automated approach to the process, and in recent years, mechanically operated film drive mechanisms have been used to transport the film through such printers. To allow stoppage of the film on a frame-by-frame basis, individual negatives have, in the past, been coded with optically readable punched holes, or codes embedded in the negative film, which are readable by various code or character recognition devices. More recently, this encoded information has been used to direct the printer to automatically print certain pre-determined package information, e.g., the number and size of a group of photographs to be printed from a specific negative.
These devices have many inherent drawbacks. Since there are a large number of manufacturers of photographic equipment, and since much older model equipment exist in the industry which is perfectly serviceable, it is desirable to provide a film drive which is easily retro-fitted to existing equipment. However, the process of retro-fitting must take into consideration the inherent space limitations (between the surface of the film plane and the lens shroud of the conventional printer, for example) while insuring that the precise distances from the film surface to the lenses used to expose the film must be maintained. Moreover, conventional film drives allow orientation of the film to the equipment in a pre-determined relationship only, that is, the longitudinal axis of a reel of negative film cannot easily be changed in relation to a photographic printer. Film shot in "portrait" format (where the vertical dimension of the developed photograph exceeds the horizontal dimension) cannot be printed in the "landscape" format (where the horizontal dimension of the print exceeds the vertical dimension).
Further, it is desirable to allow the easy removal and replacement of the pre-existing film drive mechanism, to allow the equipment owner the flexibility of returning the equipment to its original configuration.
A further drawback of existing film drives is the use of pressure feed rollers to transport the film. In this method, the film is squeezed between two compliant rollers to effectuate film transport. This method allows the presence of contaminants between the rollers to damage the surface of the film, and does not accommodate tensioning differences arising from unequal pressures placed on the film as a result of the differing diameters of film disposed on the feed and take up reels during operation.
A still further limitation of existing drives is their inability to accommodate varying widths of film, for example, 16 mm versus 35 mm film widths. Further, existing drive mechanisms cannot selectively position the film in relation to the so-called "gate" of the printer, that is, the location on the printer over which the individual negative frame is positioned prior to the actual printing process. If the film position, or the center of the subject in the frame of the negative is incorrect, there is no current mechanism for incremental altering the X or Y position of the center of the subject in the photograph so as to obtain a print which is visually balanced. Existing film drives are further limited in their ability to automatically read, decode, and act upon information encoded on or in the film negative. Typically, existing drives can only move sequentially through a series of frames, and cannot automatically locate and modify printing of frames in response to a pre-programmed set of instructions. Likewise existing film-drives have no capability of providing feed-back data to either the equipment in which they are mounted, or to other data receiving devices.
The present invention is designed to overcome these and other limitations, by providing a film-drive mechanism which is easily removable, adjustable in the X and Y axis in relation to most photographic equipment, and well-adapted to communicating with computers and computer networks.